Condensers for absorption refrigerators



March 27, 1956 R. MARTIRI CONDENSERS FOR ABSORPTION REFRIGERATORS Filed Jan. 26, 1954 Uite CON DENSERS FOR ABSORPTION REFRIGERATORS This invention refers to an improved condenser for absorption refrigerators of the type using a refrigerant, an absorbent and an inert gas in a closed fluid circulation system.

In such refrigerators, the condenser is designed to liquefy the gaseous refrigerant which, flowing from the boiler, has passed through a rectifier in which there have been eliminated the traces of the absorbent, and for supplying the liquefied refrigerant to the evaporator in which the refrigerant expands and generates the cold used for refrigeration purposes.

In most of the known absorption refrigerators the condenser is constituted by a serpentine of uniform cross section provided with cooling fins for improving the heat dissipation.

As known, at a determined temperature, the refrigerant, which is formed in most of the cases by ammonia, liquelies at a determined pressure which corresponds to the saturated vapour pressure. For instance, for an equilibrium temperature of 40 C. in the condenser, the pressure would be 14.81 atm. if the condenser included only pure ammonia. However and as already mentioned hereinbefore the absorption refrigerators also contain an inert gas, usually hydrogen, at a relatively high pressure, and this inert gas, during the inoperative state of the refrigerator, occupies all recesses of the same located above the level of liquid of the circulation system and naturally is also present in the condenser, together with a certain amount of gaseous refrigerant. 3

The presence of hydrogen at a relative high pressure i the condenser constitutes a disadvantage with respect to the general operation of the refrigerator, since now there must be generated in the condenser a higher pressure in order to make possible the liquifaction of the refrigerant at a certain temperature. Such increase in pressure affects adversely the overall efliciency of the refrigerator, and pressure measurements carried out in tubular condensers of uniform tubular cross section have shown that the gaseous refrigerant, flowing from the boiler, does not succeed in expelling completely the inert gas. This phenomenon manifests itself more strikingly when the refrigerator must operate in rooms of high temperature, since the quantity of refrigerant supplied by the boiler under such circumstances is smaller, as a consequence of the lower efficiency of the absorber on one hand, and the presence of a larger amount of gaseous refrigerant dispersed through the circulation system, on the other. Therefore, at such high temperatures the expulsion of the inert gas from the condenser is still more difiicult.

It would seem that the obvious solution for the problem should consist in the use of a tubular condenser of a very reduced uniform cross section. However such condenser cannot be used in practice, mainly in view of the fact that the volume thereof would increase disproportionately and furthermore because a conduit of reduced cross section would constitute a resistance located directly in the outlet conduit of the boiler which is of relatively ample cross section in view of the volume of gas which is generated rates atent in the boiler, and this would also affect the operation of the refrigerator.

In contraposition to this, the improved condenser according to the present invention makes it possible to obtain a more etficient and secure expulsion of the inert gas without restricting the free circulation of the gaseous refrigerant at the inlet of the condenser, and with simultaneous adaptation to the quantity of the gaseous refrigerant which decreases while the refrigerant penetrates into the condenser and liquefies.

To achieve this aim the improved condenser according to the present invention is constituted by a tube which, conveniently curved to form a serpentine, comprises at least two parts of diiferent cross sections, of which that part having the largest cross section corresponds to the inlet end of the condenser, while the part of smallest cross section corresponds to the outlet end of the condenser, the intermediate parts of the condenser if any, being arranged in the order of their decreasing cross sections in the direction of circulation of the refrigerant through the condenser.

If the condenser is of the type comprising two stages, the condenser tube is curved forming successive sections of decreasing cross sections in the direction of circulation of the gaseous refrigerant, and each of these parts can extend, totally or partially over one or more stages of the condenser.

The invention will be better understood by referring to the accompanying drawings, in which:

Fig. 1 is a plan view of a two stage condenser according to a preferred embodiment of the present invention,

Fig. 2 is a side view of the condenser of Fig. 1 along plane IIII of Fig. 1, I

Fig. 3 is a side view of the condenser of Fig. 1 along plane IIIIII of Fig, 1, and

Fig. 4 is a diagrammatic view of an absorption refrigerator constructed in accordance with the invention and showing the rectifier tube arranged at the highest level of the absorptionv refrigeration system,

In the figures, equal or like parts or elements carry the same reference numerals.

As-can be observed in the drawings, the condenser according to the present invention is connected to outlet end 1" of a rectifier constituted byan oval'tube 1, the inlet end 1 of which is joined to the outlet of the boiler B, as shown by line 19 in Fig. 1. According to the usual practice in absorption refrigerators, rectifier 1 is mounted with a slight ascending inclination in the direction of circulation of the gaseous refrigerant, indicated by arrow 2, so that outlet end 1" thereof is located at a higher level with respect to inlet end 1'.

Entrance 3 of the condenser is joined to outlet 1" of the rectifier by means of a coupling tube 4 which descends towards the upper plane of the condenser, indicated schematically by means of line 5 in Figs. 2 and 3.

In the embodiment of the condenser according to the present invention, shown in Figs. 1, 2 and 3, the same comprises solely two stages formed of tubes of different cross sections, the first of which, i. e. that connected to coupling tube 4, being constituted by a first S-shaped tube 6 of relatively large cross section which is located in upper plane 5 and constitutes the first stage of the condenser terminating at a tubular collector 7 (Fig. 3) provided with a tube 8 of very reduced cross section which forms the first outlet of liquefied refrigerant and which terminates in the evaporator E.

To collector tube 7 is joined a further coupling tube 9 which, being slightly curved upwards, extends transversely with respect to the longitudinal axis of the condenser and terminates at the inlet end 10 of the second part of the condenser, formed of a tube 11 of smaller cross section with respect to that of tube 6.

Tube 11 is U-shaped in upper plane 5 of the condenser to form a section 11a and is provided with a descending section 11b joined to a further U-shaped section 11c extending over the entire length of the condenser and located 'in a lower plane of the condenser indicated schematically by means of line 13 (Figs. 2 and 3).

' Outlet end 12 of tube 11, corresponding to the second outlet of liquified refrigerant of the condenser, is provid'ed with a collector 14 constituted by a vertical tubular recipient provided with a tube 15 for the discharge of liquefied refrigerant, also of a very reduced cross section and which terminates at the evaporator, while in its upper portion collector 14 comprises a tube 16 forming the outlet of the expelled inert gas and through which there is also discharged the non-liquefied traces of the refrigerant.

In order to facilitate the cooling of the condenser, the tubes thereof are provided with fins, and as can be seen in Figs. 2 and 3, tubes 6 and 11a of the condenser, corresponding to the upper plane 5 of the same, are in thermal contact with a plurality of fins 17, While tube lie of the lower plane 13 is provided with fins 18.

The cooling of the condenser according to the present invention is still more improved due to the fact that the tubes of the same are curved in such a manner that their longitudinal portions are mounted freely in the upward stream of cooling air, as can be observed in Fig. 1.

The condenser according to the present invention, shown schematically in Figs. 1, 2 and 3, comprises two stages, each of which consists of a serpentine of uniform cross section. However, it will be understood that the condenser according to the present invention may comprise tWo or more parts of different cross sections constituting, nevertheless, a sole condensation stage. It is also possible to design the condenser in such a manner that said parts of different cross section extend over more than one stage of the condenser. Fig. 4 includes, as is common practice in known absorption refrigeration systems, an absorber A in communication with an evaporator E, and a collector C in communication with the absorber A, on the one hand, and the boiler B, on the other hand. As can be seen in Fig. 4, the rectifier tube 1 is arranged at the highest level of the absorption refrigeration system. In general, the invention is not to be limited to the particular elements that have been disclosed, since these are illustrative, but the scope of the invention is indicated in the claim.

What I claim is:

In an absorption refrigerator comprising a straight rectifier tube having an inlet end and an outlet end and arranged at the highest level of the absorption refrigeration system with a slightly ascending inclination towards said outlet end, a condenser constituted of a first tube of substantially uniform cross-section coiled in a substantially horizontal plane located below said rectifier tube, in the form of a flattened S formed of a substantially straight inlet portion, a substantially straight middle portion and a substantially straight outlet portion, means interconnecting the outlet end of said rectifier tube with said inlet portion of said first coiled tube, said inlet and middle portions of said first coiled tube extending substantially over half of the longitudinal extension of said rectifier tube, While said outlet portion extends over substantially the entire length of said rectifier tube, a second tube of substantially uniform. and smaller cross-section coiled to form a first U-section located in the plane of said first coiled tube in the space comprised between the free end of the outlet end of said first tube and said rectifier tube and a second U-section extending in a lower horizontal plane with respect to said first coiled tube and said first U-section, one arm of said second U-section of said second coiled tube being arranged between the arms of said first U-section of said second coiled tube and said inlet and middle portions of said first coiled tube, While the other arm of said second U-section is arranged between said middle and outlet portions of said first coiled tube, a coupling tube of gradually decreasing cross-section joining the outlet end of said outlet portion of the first coiled tube to the inlet end of the first U-shaped section of said second coiled tube and arranged perpendicularly with respect to the straight portions of the first and second coiled tubes, a first set of cooling vanes arranged on the straight portions of the first coiled tube and on the straight portions of the first U-shaped section of the second coiled tube, and a second set of cooling vanes arranged on the straight arms of the second U-shaped section of said second coiled tube, said vanes being arranged in substantially parallel planes extending perpendicularly to the longitudinal axes of the respective straight portions of the coiled tubes.

References Cited in the file of this patent UNITED STATES PATENTS 954,575 Lang Apr. 12, 1910 2,193,460 Lavigne Mar. 12, 1940 2,241,186 Coons May 6, 1941 FOREIGN PATENTS 671,630 Germany Jan. 26, 1939 

